1. Field of the Invention
The present invention relates generally to shear resistant steel decking, and more particularly, to an apparatus for forming a shear-resistant side lap seam attachment in steel decking.
2. Description of the Relevant Art
It is common in the construction of commercial buildings to create floors and roofs from steel deck panels. Such steel deck panels might include ribbed, or “fluted”, steel deck panels as well as cellular steel deck panels. Examples of fluted steel deck panels are shown, for example, in U.S. Pat. Nos. 4,186,535 and 4,894,967. Such steel deck panels are typically welded to underlying structural support beams, although mechanical fasteners, such as power-actuated pins or screws may also be used. When properly assembled, such fluted steel deck panels provide a cost-effective diaphragm for forming floors and roofs of commercial buildings. These steel deck panels are often referred to in the trade by the names A-deck, B-deck, F-deck, N-deck, W-deck, etc. Such panels are often provided in different thicknesses, or gauges, ranging from relatively thin 22 gauge stock to more rigid 16 gauge stock. Panel widths are typically 24 inches to 36 inches, depending upon the type of steel deck being used. Individual panel lengths can vary from as little as three feet to over 40 feet. Reinforcing ribs, or “flutes”, are formed in such panels. One edge of each such panel, extending parallel to such ribs, includes an upwardly-extending lip. The opposite edge of the panel includes a downwardly-extending inverted U-shaped lip for extending over, and receiving, the upwardly-extending lip of an adjacent panel to form a seam. The two adjacent panels are attached along such seam. Various methods have been used to form the seam attachment, including button punching, crimping, screwing, riveting, welding, as well as shearing and deformation of the deck seam.
Building codes of many geographic areas require buildings to be able to withstand lateral shear forces of specified minimums. This is particularly true for regions known to be subject to high winds (e.g., the Eastern United States), earthquakes or other seismic activity (e.g., the Western United States). Steel roof decks, when properly secured to the underlying building frame, form a diaphragm. In order for the diaphragm to resist lateral shear forces without failure, the seam attachment securing the sides of adjacent panels to each other must be able to effectively resist relative sliding movement of adjacent panels along the seam joining the two panels. Often, side-lapped joints of a steel deck diaphragm must be inspected for consistency and integrity before further construction of a building may proceed. To avoid construction delays, such side-lapped joints should be formed in a manner that allows such joints to be inspected quickly and easily, preferably from the top side of the decking.
Each different seam attachment method presents benefits and disadvantages. For example, button punch tools for deforming “buttons” within the overlapped lips of adjacent panels along the side seam are relatively easy to use, and a number of such attachments can be formed in relatively little time. One such pneumatically-assisted tool for crimping and dimpling the side seam of steel decking is disclosed in U.S. Pat. No. 5,878,617 to Parker. However, such button punches do not form a very secure connection, and are not very effective at resisting lateral shear forces.
Other seam attachment tools actually shear and deform portions of the seam. For example, in U.S. Pat. No. 182,193 issued in 1876, Holeton discloses a method of forming triangular notches in the side-lapped joint and then folding over such triangular notches to interlock the joint. In U.S. Pat. No. 3,641,729, inventor Irvin discloses the use of lip-clenching dies operated by a clinching tool to cut a slit through the side-lapped joint, and to form opposing lobes for securing the side-lapped joint.
U.S. Pat. No. 6,212,932 to Parker discloses a pneumatic shear for forming structural louvers. In one embodiment, a pneumatically-operated tool selectively opens and closes a pair of jaws that are pivotally connected to each other about a common pivot axis. One such jaw includes a single blade having first and second opposing sides forming first and second blunt edges. The second jaw includes two spaced blades that are spaced from each other by the thickness of the single blade on the first jaw, also having blunt edges. Thus, the two spaced blades on the second jaw form a “die” for receiving the single blade on the first jaw when the first and second jaws are pivoted to their closed position. With the jaws in their opened position, the first and second jaws are inserted over a side-lapped seam of a steel deck. The pneumatic tool is then activated to close the jaws toward each other. The single blade of the first jaw passes between the two “die” blades of the second jaw, forming a pair of cuts in the overlapped seam. Further closing of the jaws deforms a central tab in a first direction, while deforming regions on either side of the central tab in the opposite direction. Side-lapped joints formed by use of this apparatus have been shown to securely fasten the side-lapped seams and to satisfactorily resist deformation due to horizontal shear loading.
In U.S. Pat. No. 7,434,314, issued to Morton, a further tool for reliably fastening together side-lapped edges of adjacent deck panels is disclosed. The '314 patent describes a seam attachment tool that includes four jaws, two of which are positioned on one side of the seam, and the other two of which are positioned on the opposite side of the seam. Two of the opposing jaws cooperate with each other to shear a first cut line through the seam. The other two opposing jaws cooperate with each other to shear a second cut line through seam parallel to, and slightly spaced apart from, the first cut line. The material bounded between the first and second cut lines forms a louver or tab. This material is deformed in a first direction adjacent the first cut line, and deformed in the opposite direction adjacent the second cut line. It has been found that prototypes of the seam attachment tool disclosed in the '314 Morton patent form a relatively secure seam attachment, and attain significantly higher shear resistance values than other known punching tools.
Applicant has more recently come to realize that the four-jaw punch tool disclosed in the '314 patent could be further improved. For example, the aforementioned four-jaw tool is not perfectly symmetrical. As a result, when a deck installer triggers the pneumatic actuator on a working prototype of such tool, a torque, or twisting motion, is applied to the handle of the tool, which the operator must resist. Since the deck installer typically makes many of such attachments continuously along the deck seam on a roof, the hands, wrists, and arms of the deck installer can tire easily. In addition, it was found that, when using the working prototype, the jaws of the four-jaw tool would sometimes bind in the deck seam, even after pneumatic pressure was released from the actuator of the tool. This binding of the jaws may be due to the torque exerted upon the seam by the jaws in a non-symmetrical fashion.
One of the stated objects of the invention set forth in the specification of the '314 patent is to provide a punching tool having a blade assembly that equalizes the wear on the blades, and which avoids excessive stress on any particular blade, to extend the usable life of the tool. Applicant has found that, in regard to the aforementioned working prototype, though the addition of the fourth jaw lessened the likelihood of jaw failure, it did not eliminate the problem of jaw failure. When one or more of the jaws fail, the punching tool must essentially be disassembled; the jaw with the broken blade must be detached from the actuator and replaced with a new jaw having a fresh blade. Apart from the need to keep the rather bulky replacement jaws on hand for such instances, significant time is required to disassemble the tool and repair it. During such down time, work on attaching the deck seam necessarily halts. Jaw failure can be reduced somewhat by using a harder steel to form the jaw; however, making the entire jaw from specially hardened steel significantly increases the cost of the tool; it also makes the entire jaw assembly more brittle, which allows for failures in the jaw at points other than the working blade end.
Accordingly, it is an object of the present invention to provide a punching tool for forming an attachment in an interlocking side-lapped seam of a steel deck structure which provides a solid attachment capable of resisting significant horizontal shear loads.
It is a further object of the present invention to provide such a punching tool which can be operated relatively quickly and easily by a deck installer to attach interlocking side-lapped seams of a steel deck structure.
It is a still further object of the present invention to provide such a punching tool which produces an attachment that can be quickly and easily inspected by an inspector standing atop the assembled steel decking.
Another object of the present invention is to provide such a punching tool having jaws that generally equalize the wear on the blades of such jaws, and which avoids excessive stress on any particular blade, to extend the usable life of the tool.
A yet further object of the present invention is to provide such a punching tool which can be repaired quickly and easily if a blade formed on the working end of the jaw should break.
Still another object of the present invention is to form a side-lapped seam attachment that provides higher shear values by forming an attachment which is more resistant to slippage when subjected to a horizontal load along the longitudinal axis of the side-lapped seam.
A still further object of the present invention is to provide such a punching tool which is less likely to bind in the deck seam following actuation of the tool and subsequent release of compressive forces upon the jaws of the tool, to facilitate easier disengagement of the tool from the deck when air pressure on the tool is released.
Yet another object of the present invention is to provide such a punching tool wherein the jaw assembly is symmetrical in nature, and wherein there is no twisting torque force exerted upon the tool handle as the punch tool is actuated.
These and other objects of the invention will become more apparent to those skilled in the art as the description of the present invention proceeds.